Question

I’m running into an issue with the DecimalConverter and Int32Converter classes, which seem to be returning inconsistent results, as demonstrated by the following simple console program:

using System;
using System.ComponentModel;

class App
{
    static void Main()
    {
        var decConverter = TypeDescriptor.GetConverter(typeof(decimal));
        Console.WriteLine("Converter: {0}", decConverter.GetType().FullName);
        Console.WriteLine("CanConvert from int to decimal: {0}", decConverter.CanConvertFrom(typeof(int)));
        Console.WriteLine("CanConvert to int from decimal: {0}", decConverter.CanConvertTo(typeof(int)));

        Console.WriteLine();

        var intConverter =  TypeDescriptor.GetConverter(typeof(int));
        Console.WriteLine("Converter: {0}", intConverter.GetType().FullName);
        Console.WriteLine("CanConvert from int to decimal: {0}", intConverter.CanConvertTo(typeof(decimal)));
        Console.WriteLine("CanConvert to int from decimal: {0}", intConverter.CanConvertFrom(typeof(decimal)));
    }
}

The output from this is as follows:

Converter: System.ComponentModel.DecimalConverter
CanConvert from int to decimal: False
CanConvert to int from decimal: True

Converter: System.ComponentModel.Int32Converter
CanConvert from int to decimal: False
CanConvert to int from decimal: False

Unless I’m understanding TypeConverters incorrectly, the following should hold true:

TypeDescriptor.GetConverter(typeof(TypeA)).CanConvertFrom(typeof(TypeB))

should give the same result as

TypeDescriptor.GetConverter(typeof(TypeB)).CanConvertTo(typeof(TypeA))

At least in the case of System.Int32 and System.Decimal, they do not.

My question is this: Does anybody know if this is by design? Or are the TypeConverters for native types in C# actually broken?

Answer 1

According to the MSDN documentation for Int32Converter…

This converter can only convert a 32-bit signed integer object to and
from a string.

I agree with @svick in the comments, though, I’m not understanding why you would need to deserialize a JSON string through Int32 to a Decimal in the first place.